Nucleophilic de-coordination and electrophilic regeneration of "hemilabile" pincer-type complexes: Formation of anionic dialkyl, diaryl, and dihydride Pt-III complexes bearing no stabilizing pi-acceptors

作者：Poverenov E; Gandelman M; Shimon LJW; Rozenberg H; Ben David Y; Milstein D^*

来源：Chemistry - A European Journal, 2004, 10(19): 4673-4684.

DOI：10.1002/chem.200400514

• hemilabile complexes hydrides
• N,P ligands
• pincer ligands
• platinum

Novel anionic dialkyl, diaryl, and dihydride platinum(II) complexes based on the new "long-arm" hemilabile PCN-type ligand C6H4[CH2P(tBu)(2)](CH2)(2)N(CH3)(2) with the general formula Li+ [Pt(PCN)(R)(2)](-) (R = Me (4), Ph (6) and H (9)) were prepared by reaction of [Pt(PCN)(R)] complexes (obtained from the corresponding chlorides) with an equivalent of RLi, as a result of the opening of the chelate ring. Alkylating agents based on other metals produce less stable products. These anionic d(8) complexes are thermally stable although they bear no stabilizing a acceptors. They were characterized by H-1, P-31{H-1}, C-13, and Li-7 NMR spectroscopy; complex 9 was also characterized by single crystal X-ray crystallography, showing that the Li+ ion is coordinated to the nitrogen atom of the open amine arm and to the hydride ligand (trans to the P atom) of a neighboring molecule (H-Li = 2.15 Angstrom), resulting in a dimeric structure. Complexes 4 and 9 exhibit high nucleophilic reactivity, - - pincer upon which the pincer complex is regenerated. Reaction of 4 with water, methyl iodide, and iodobenzene resulted in the neutral complex [Pt(PCN)(CH,)] (3) and methane, ethane, or toluene, respectively. Labeling studies indicate that the reaction proceeds by direct electrophilic attack on the metal center, rather than attack on the alkyl ligand. The anionic dihydride complex 9 reacted with water and methyl iodide to yield [Pt(PCN)(H)] (8) and H-2 or methane, respectively.

• 出版日期2004-10-4